1. Field of the Invention
The present invention relates generally to particle accelerators and, ore particularly, to particle accelerators for producing collisions between particles contained within a predetermined system.
2. Related Prior Art
The present invention is related to the field of machines known as article accelerators and which include cyclotrons, microtrons, linear accelerators and inertial electrostatic confinement (IEC) machines. Following is a brief summary of the general characteristics of each of these prior art machines:
(a) Cyclotronsxe2x80x94a cyclotron 1 (see FIG. 1) is comprised of two semicircular hollow boxes, called xe2x80x9cdeesxe2x80x9d 2, 4 which are formed of an electrically conductive material, such as copper, and which are arranged with the flat, open sides of the dees 2, 4 separated and facing each other. The dees 2, 4 are located in an evacuated chamber having a very high vacuum, and are located between the poles of a strong magnet, which generates an essentially uniform magnetic field passing through the flat faces, i.e. the top and bottom, of the dees 2, 4 and through the entire volume of the dees 2, 4. An alternating voltage is applied between the dees 2, 4. Ions or other charged particles, are introduced to the cyclotron at a central location between the dees 2, 4. The charged particle introduction or generation is controlled such that essentially all particles are accelerated to the maximum cumulative energy achievable by the particular cyclotron, and essentially all charged particles introduced or generated leave the acceleration chamber as part of the product beam. The paths of the charged particles within each dee 2, 4 are semicircles centered at the center of the acceleration chamber wherein each time a particular particle crosses between the dees 2, 4, it is accelerated to a higher energy, and the radius of its path is thereby increased to correspond to the higher energy, such that the paths of the particles within the cyclotron approximate a spiral. The dee to dee accelerating voltage is selected to be such that the increase in path radius resulting from each acceleration is great enough to provide spacing between the paths of particles which have undergone different numbers of accelerations, and thereby to prevent collisions of particles of one energy with those of greater or lesser energies.
(b) Microtronsxe2x80x94microtrons are machines which accelerate electrons in a vacuum chamber from which the accelerated electrons are extracted as a beam for use with an external target. The acceleration chamber of the basic circular microtron is in a magnetic field (similar to that of a cyclotron) which causes the electrons to move in circular paths. An electron generator and a radio frequency (i.e., microwave frequency) resonant cavity are located at a point near the wall of the circular acceleration chamber. Electrons from the generator are injected into the resonant cavity and accelerated by radio frequency energy. They leave the cavity and travel in a circular path wherein the magnetic field strength and microwave frequency are selected such that the length of the electrons circular path is an integral number of wavelengths at the selected frequency, such that the electron re-enters the resonant cavity in phase with the cavity frequency, and it is then again accelerated as it passes through the cavity. The next orbit of the electron is again circular, but has a greater radius than the first path, and has a total length which is a new and greater multiple of wavelengths. This sequence continues with the electron passing through the resonant cavity and being accelerated once each orbit, until the radius of the orbit is close to that of the acceleration chamber, at which time the electron is extracted from the chamber as part of a beam, and is directed to a target outside of the acceleration chamber. As with the cyclotron, microtrons operate with a high vacuum acceleration chamber and are provided with a single fixed location of charged particle generation.
(c) Linear Acceleratorsxe2x80x94linear particle accelerators use electric fields to accelerate charged particles in a straight line in a vacuum. The particles are generated at a fixed location at one end of an accelerator chamber and are accelerated in a beam into a target at the other end. Electrical and/or magnetic fields are used to prevent the charged particle beam from spreading out, which would normally occur due to electrical repulsion of the particles away from each other. Single or multiple acceleration stages may be used, and most machines employ multiple stages with accelerating voltages between stages. Further, most machines require very high voltages for acceleration.
(d) Inertial Electrostatic Confinement (IEC) Machinesxe2x80x94IEC machines have been developed in two geometries, spherical and cylindrical. Both types have been used for neutron generation using deuteriumxe2x80x94deuterium (Dxe2x80x94D) and/or deuterium-tritium (D-T) reactions. The operating concept for the spherical type of the IEC machine includes providing a hollow electrically conductive outer spherical chamber, and a smaller spherical hollow grid formed of a conductive material which is centered within the spherical chamber. The chamber contains deuterium or a deuterium-tritium mix at a pressure somewhat less than about 2 mm Hg. A high DC voltage is applied between the outer chamber and the grid, with the grid being negatively charged. The voltage is high enough to cause breakdown of the gas within the chamber, creating ions and/or plasma. IEC machines typically use voltages ranging from 16,000 to about 40,000 volts, with higher voltages being desirable. The positive deuterium and/or tritium ions are accelerated radially inwardly toward the negatively charged grid, where they reach maximum energy, pass through holes in the grid, and travel across the space inside the grid at constant speed, after which they pass out of the grid through holes in the opposite side. At this point, the positively charged ion is traveling toward the positively charged outer sphere, which repels it. The ion is slowed to zero radial velocity and is then re-accelerated toward the negatively charged grid. The cycle repeats indefinitely until the ion impacts another ion, a non-ionized gas atom, or a solid part of the grid sphere. Neutrons are generated from ionxe2x80x94ion and ion-gas collisions. The ion energies and electrical fields are such that ions cannot reach the outer sphere, so that the surface of this sphere cannot be used as a target.
The cylindrical IEC machine is similar to the spherical IEC machine in principle and consists of a conductive tube and two slightly concave conductive reflectors, one at each end of the tube and separated from the tube by a predetermined distance. The operative elements of the machine are enclosed in a chamber which contains deuterium or a mixture of deuterium and tritium at a pressure similar to that used in the spherical IEC machine. High voltage sufficient to cause gas breakdown is applied between the tube and the reflectors, with the tube negative and each reflector positive, to cause the gas to break down and produce ions in the regions between the tube and the reflectors. The ions are initially accelerated toward the negatively charged tube, pass through it, and are slowed and then reversed and re-accelerated back toward the tube by the reflector. The ions continue to travel back and forth through the tube until they collide with another ion or neutral gas atom. Both IEC machines accelerate ions by single stage electrostatic means, which requires very high voltage. For example, to accelerate a deuteron to a maximum energy of 22 Kev, 22,000 volts must be applied between the outer sphere and the grid in the spherical IEC machine, or between the tube and reflectors in a cylindrical IEC machine.
While the above described machines provide effective means for accelerating particles to perform their desired functions, there exists a continuing need for a particle accelerator machine which is capable of operating at lower voltages than prior art machines and is capable of performing work by inducing particle-to-particle collisions within the machine, including production of neutrons and to produce energy as a result of such collisions, as well as other useful operations which may be obtained through collision of particles therein.
The present invention is configured with essentially the same physical components as that of a cyclotron in that the present invention includes two hollow dees of electrically conductive material which are separated and electrically insulated from each other with the flat, open sides of the dees facing each other. The dees are located between the poles of a strong magnet which generates an essentially uniform magnetic field through the flat faces, i.e. the top and bottom, of the dees. In addition, the dees are connected to an oscillator for providing an alternating voltage between the dees.
The dees for the particle accelerator of the present invention are located within a chamber wherein the chamber contains gaseous deuterium (hydrogen-2) or tritium (hydrogen-3), or a mixture of the two, provided at a measurable pressure. Further, other gases, in addition to or in place of deuterium or tritium, may be provided to the chamber. Thus, in a broad aspect of the present invention, the particle accelerator disclosed herein differs from a cyclotron in that a cyclotron requires an evacuated chamber, and the present invention purposefully provides a gas filled chamber for reasons to be described below.
In a further aspect of the invention, ions are introduced to the chamber for acceleration within the hollow areas defined by the dees. Specifically, an ion introduced into the area between the dees will have a positive charge and will be attracted to the negatively charged dee, and therefore will be accelerated toward this dee. Once the ion enters the dee, it will no longer xe2x80x9cseexe2x80x9d the electric field and will move at a constant speed, but will travel in a circular path due to forces caused by the magnetic field. By the time the ion has traveled half a circle and moves toward the opposite dee, the voltage between the dees will have been reversed, so that the opposing dee is now negatively charged to again accelerate the ion. Due to the increasing speed of the ion, the ion will follow an essentially spiral path of increasing radius.
In an important aspect of the present invention, ions may be formed within the chamber from the gas contained therein, and additionally may also be fed to the chamber from an outside source. Production of the ions may be accomplished by spaced electrodes located between the dees and defining an electrical potential to ionize gas therebetween. As the ions are accelerated in spiral paths within the dees, they will collide with non-ionized deuterium and/or tritium atoms within the acceleration chamber, and with other deuterium and/or tritium ions, whether accelerated or not. As a result of deuteriumxe2x80x94deuterium (Dxe2x80x94D) and/or deuterium-tritium (D-T) collisions and the resultant nuclear reactions, and in accordance with an aspect of the present invention, neutrons will be generated. Further, in addition to the targets provided by the atoms and ions moving within the chamber, additional targets may be deuterium and/or tritium atoms affixed to the surfaces of the chamber by chemical means (such as hydrides), by surface adsorption or absorption and/or by collision induced absorption.
In accordance with an additional aspect of the invention, ions are produced at locations other than adjacent to the geometric center of the device, for example, through collision of ions with neutral atoms to form additional ions. Thus, it is an object of the present invention to provide ions following paths which are not concentric with each other, whereby collisions between accelerated ions will occur of sufficient energy to cause nuclear reactions between the colliding particles.
In a further aspect of the invention, the particle accelerator may be configured as an ion pump or low pressure gas pump. In such a configuration, each of the dees would be provided with one or more tubes wherein each tube is attached with its axis tangential to the respective dee. The tubes on one dee are positioned such that neutral atoms which are struck by accelerated ions are xe2x80x9cknockedxe2x80x9d into the tube openings, and the tubes attached to the other dee are positioned such that struck atoms are propelled away from the opening, decreasing the number of atoms in this region and thus reducing the pressure to induce a gas flow through the tube into the chamber. In this manner, the atoms contained within the particle accelerator may be replenished to avoid depletion of the target atoms during operation of the particle accelerator.
In a further aspect of the invention the particle accelerator may be used as a gas separator/purifier wherein a mixture of gases is provided to the particle accelerator and, for a specific magnetic field strength, the frequency of the alternating voltage applied across the dees is selected such that the ions of one of the gases will have the correct charge-to-mass ratio to be accelerated each time they cross the dees, whereas the ions having other charge to mass ratios will not be accelerated within the chamber. The accelerated ions will eventually be accelerated to the outer perimeter of one of the dees having an exit tube whereby the accelerated ions may be selectively extracted from the chamber.
In accordance with a further aspect of the invention, modifications to the configuration and spacing of the dees may be provided in order to enhance the number of head-on and near-head-on collisions between particles as they travel between the dees as well as modifications to direct accelerated ions to paths of travel between the outside perimeter of the dees and the inside surface of the gas containing chamber in order to permit the accelerated ions to travel for an extended time to increase the probability of a collision between the ion and an atom contained within the chamber.